1. Field of the Invention
The present invention relates to a substrate hold apparatus which is used in, for example, an ion implantation apparatus, an etching apparatus and a thin film forming apparatus and includes an electrostatic chuck for electrostatically attracting and holding a substrate thereon, and also relates to a method for judging the state of the substrate when it is pushed up using a push-up member after cutting off an applied voltage to the electrostatic chuck.
2. Description of the Related Art
In the below-cited Japanese Patent No. 3814905 (paragraphs 0010-0012, FIGS. 2-5), there is disclosed a substrate hold apparatus which includes an electrostatic chuck for electrostatically attracting and holding a substrate (for example, a semiconductor substrate) thereon, a push-up member contactable with a position of vicinity of an edge of the substrate on the electrostatic chuck from below for pushing up the substrate, and a drive apparatus for driving at least one of the electrostatic chuck and push-up member to thereby allow the push-up member to push up the substrate.
Even when the applied voltage to the above-mentioned electrostatic chuck is cut off after the substrate is attracted to the electrostatic chuck, for a certain period of time, electric charges remain between the electrostatic chuck and substrate, thereby generating a residual attracting force. Suppose the residual attracting force is large, when the substrate is removed from the electrostatic chuck, there are caused inconveniences in the substrate, for example, the substrate is caused to bounce, or to be shifted in position, or to be broken.
As means for preventing the generation of such inconveniences, in the below-cited JP-A-2004-119792 (paragraphs 0034, 0042, 0043, FIGS. 1 and 5), there is disclosed a technology in which there is provided a residual attracting force detect portion for detecting, as a residual attracting force, a load applied to a lift pin used to push up and remove the substrate from below, it is checked whether the detected residual attracting force is larger than a given value or not, and, when it is found larger, the processing is made to go to a different residual electric charge removing operation from an originally specified substrate processing operation. Specifically, a conductive wafer for removing residual electric charges is carried onto the electrostatic chuck, the conductive wafer is grounded to remove the residual electric charges, and, after then, the conductive wafer is taken out.
According to the technology disclosed in the above-cited JP-A-2004-119792, it is checked through a single residual attracting force judgment whether the residual attracting force is abnormal (that is, the residual attracting force is larger than a given value) or normal (that is, the residual attracting force is smaller than a given value). When it is found abnormal, immediately, the processing goes to a residual electric charge removing operation which is different from an originally specified substrate processing operation. However, when the processing goes to the residual electric charge removing operation, the originally specified substrate processing operation cannot be carried out during the time. This raises a problem that the throughput of the substrate (the processing performance of the substrate per unit time) is lowered greatly.
Also, according to in the JP-A-2004-119792, when it is judged that a residual attracting force (specifically, a load applied to the lift pin) detected by the residual attracting force detect portion is smaller than a given value, the processing as it goes to the originally specified substrate processing operation. However, when a detecting system (a sensor system) is abnormal or the substrate is abnormal, for example, when a load to be detected originally cannot be detected due to the abnormal state of the detecting system, or when the position of the substrate is shifted greatly on the electrostatic chuck and the load applied to the lift pin is thereby small, the load applied to the lift pin cannot be detected.